Vasospasm, its role in the pathogenesis of diseases with particular reference to the eye

Iris transillumination defects in patients with primary open angle glaucoma

PURPOSE

To examine the incidence and pattern of iris transillumination defects in patients with primary open angle glaucoma (POAG) with and without vascular dysregulation, in comparison to controls.

METHODS

We prospectively examined 24 patients with POAG (M/F 10:14; mean age 59 +/- 14, range 21-76 years) and 23 controls (M/F 10:13; mean age 52 +/- 15, range 25-86 years). Vascular dysregulation was presumed if patients had a typical medical history of vasospasm and a pathological result in nailfold capillaroscopy. Iris transillumination defects were visualized by video-taped, digitized diaphanoscopy and assessed by two blinded observers.

RESULTS

We found significantly more iris transillumination defects in POAG than in controls (54.2% vs. 8.7%; chi2 = 8.85; df = 1; p = 0.002). The defects in POAG showed a characteristic radially-streaked pattern different from those described, for instance, in pigment dispersion syndrome, pseudoexfoliation syndrome, and acute glaucoma. Glaucoma patients with vascular dysregulation had a tendency to a higher incidence of transillumination defects than non-vasospastic patients, though this finding was not significant.

CONCLUSIONS

Patients with POAG have a higher incidence of iris transillumination defects than controls. The underlying mechanisms are not yet clear and call for further investigation.

Peripheral vasospasm and nocturnal blood pressure dipping--two distinct risk factors for glaucomatous damage?

PURPOSE

To evaluate the relationship between peripheral vasospasm and circadian blood pressure rhythm in patients with primary open angle glaucoma (POAG).

METHODS

Nail-fold capillaroscopy, combined with a cold provocation test, and 24-hour blood pressure monitoring was carried out in 130 patients with POAG (M:F 58:72; mean age 60 +/- 14 years), 99 with high-tension glaucoma (HTG) and 31 with normal-tension glaucoma (NTG). Peripheral blood flow parameters were compared for patients with a nocturnal fall in mean systemic blood pressure (MBP) of less than 10% (non-dippers), patients with a nighttime MBP fall of 10-20% (dippers), and patients with a nighttime MBP fall of more than 20% (over-dippers).

RESULTS

Patients with POAG showed a significantly lower blood flow velocity both at baseline (p < 0.01) and after cold provocation (p < 0.02) and a significantly higher percentage of cold-induced blood-flow standstill (p < 0.0001) in the nail-fold capillaroscopy than normal controls. The numbers of non-dippers (50), dippers (66) and over-dippers (14) did not differ between the HTG and NTG group. There were no significant differences between non-dippers, dippers, and over-dippers in peripheral blood flow parameters.

CONCLUSIONS

Our findings indicate that vasospasm and low blood pressure may be distinct risk factors for glaucomatous damage. It also appears that screening for vascular dysregulation and systemic hypotension should not be restricted to NTG patients alone.

Ophthalmologic migraine

A fair portion of the diagnostic practice of the neurologist and ophthalmologist involves the deciphering of visual symptoms in patients known to have migraine, and many who at the time of their initial presentation do not. The most common visual disorder in this category, migraine with aura, has been studied extensively, but no conclusive evidence has been proven linking the visual aura, believed to result from a spreading depression, to the subsequent development of the cephalgia. Vasospasm remains controversial in the pathophysiology of migraine, but may play a role in patients who suffer more permanent or complicated neurovisual dysfunction. This paper reviews some of the current thoughts on the subject, and hopefully will stimulate the reader to explore the complex issue of this common malady.

The impact of ocular blood flow in glaucoma

Two principal theories for the pathogenesis of glaucomatous optic neuropathy (GON) have been described--a mechanical and a vascular theory. Both have been defended by various research groups over the past 150 years. According to the mechanical theory, increased intraocular pressure (IOP) causes stretching of the laminar beams and damage to retinal ganglion cell axons. The vascular theory of glaucoma considers GON as a consequence of insufficient blood supply due to either increased IOP or other risk factors reducing ocular blood flow (OBF). A number of conditions such as congenital glaucoma, angle-closure glaucoma or secondary glaucomas clearly show that increased IOP is sufficient to lead to GON. However, a number of observations such as the existence of normal-tension glaucoma cannot be satisfactorily explained by a pressure theory alone. Indeed, the vast majority of published studies dealing with blood flow report a reduced ocular perfusion in glaucoma patients compared with normal subjects. The fact that the reduction of OBF often precedes the damage and blood flow can also be reduced in other parts of the body of glaucoma patients, indicate that the hemodynamic alterations may at least partially be primary. The major cause of this reduction is not atherosclerosis, but rather a vascular dysregulation, leading to both low perfusion pressure and insufficient autoregulation. This in turn may lead to unstable ocular perfusion and thereby to ischemia and reperfusion damage. This review discusses the potential role of OBF in glaucoma and how a disturbance of OBF could increase the optic nerve's sensitivity to IOP.

Endothelin: is it a contributor to glaucoma pathophysiology?

Endothelin is a vasoactive peptide that has been shown to play an important role in vascular homeostasis. Recently, endothelin and its receptors have been found in ocular tissues where it appears to have a regulatory function. Endothelin is found in both the aqueous and vitreous humors and its concentration is elevated in glaucoma patients and in animal models of glaucoma. In the current review, the authors present information about the distribution of endothelin and endothelin receptors in the eye and the ocular actions of endothelins. Specifically, endothelin/aqueous humor dynamics, endothelin/nitric oxide interactions, endothelin and ischemia, and endothelin/optic nerve head effects. Observations concerning the potential role of endothelin in glaucoma pathophysiology is presented and discussed relative to its effects on the optic nerve head and in relation to glaucoma theories.

Increased endothelin-1 plasma levels in giant cell arteritis: a report on four patients

PURPOSE

To test the hypothesis that endothelin-1 is increased in giant cell arteritis.

METHODS

Interventional case series. The medical history of four patients who presented to the University Eye Clinic Basel, Switzerland, with giant cell arteritis is reported. Endothelin-1 plasma levels were measured in all patients. The relevant medical literature was reviewed.

RESULTS

All patients presented with typical histopathological signs of giant cell arteritis in the temporal artery biopsy. The erythrocyte sedimentation rate was increased in two patients. All patients showed significantly increased endothelin-1 plasma levels, ranging between 3.13 to 4.82 pg/ml (reference value for females: 1.42 pg/ml +/- 0.28 standard deviation, for males: 1.67 pg/ml +/- 0.34 standard deviation).

CONCLUSION

The data obtained from the patients so far examined indicate that the level of circulating endothelin-1 is increased in giant cell arteritis. The clinical relevance of such an increase needs to be further evaluated.

Cold feet and prolonged sleep-onset latency in vasospastic syndrome

People with vasospastic syndrome have cold hands and feet and abnormal vasoconstriction after local cold exposure. Normally there is a circadian rhythm of distal vasodilation, with onset in the early evening, which directly influences ability to fall asleep. We gave a sleep questionnaire to 32 patients with primary vasospastic syndrome and 31 healthy controls. People with vasospasticity had significantly prolonged sleep-onset latency both at onset of night-time sleep and after nocturnal disturbance. This prolonged latency could be associated with impaired capacity for distal vasodilation.

Susac syndrome: a vasospastic disorder?

PURPOSE

The Susac syndrome is a microangiopathy that leads to visual symptoms, hearing loss and neurological symptoms.

CASE REPORT

We report on a young woman suffering from this syndrome who also presented the following signs and symptoms typical of a vasospastic syndrome; 1) a history of cold hands, low blood pressure and migraine; 2) a typical alteration of conjunctival vessels; 3) prolonged flow arrest time after cooling in nailfold capillaromicroscopy; 4) increased resistivity in the orbital vessels measured by color Doppler imaging; and 5) an increased plasma level of endothelin-1.

CONCLUSIONS

We postulate that the Susac syndrome is a manifestation of the vasospastic syndrome.